A simplified computational approach to account for fluid-structure interaction effects on blast-loaded plates in EUROPLEXUS

This report explores a simplified approach to account for Fluid-Structure Interaction (FSI) effects on blast-loaded plates. Basically, the model estimates the effect of plate motion and deformation on the blast pressure acting on the plate. The basic ingredient of the model is the time history of the on-plate blast pressure (incident plus reflected) that would be applied on the plate if this would be rigid and fully blocked. This is referred to as the rigid pressure and can be obtained either from theoretical considerations, or from analytical expressions, or from an experiment performed in a shock tube using a closed rigid end. Then, the model uses thermodynamic assumptions and relations to estimate the modification in the applied pressure induced by the motion and deformation of the plate, thus obtaining the effective Fluid-Structure Interaction pressure. This pressure is equal to the rigid pressure for zero velocity of the plate, it is smaller than the rigid pressure for a plate velocity directed along the incoming shock, and it is larger than the rigid pressure if the plate moves towards the incoming shock. The effective Fluid-Structure Interaction pressure is then used to load the plate and to compute its dynamic behaviour within the EUROPLEXUS fast transient Finite Element code. When this simplified FSI model (SFSI) is used, there is no need to include the fluid in the numerical model, so only the structure is discretized. This allows for a huge saving in computer time for a given simulation. The method reasonably applies only to relatively simple geometrical configurations of the loaded structure, where multiple wave reflections and other complex fluid-dynamic effects such as channelling may be excluded a priori. However, such cases have a large practical interest and it may be useful to be able to model them, albeit with some approximation, by a very fast numerical model, so as to be able to carry out parametric studies, for example.